Cathode ray oscillograph control



1935. w. F. SKEATS 1,986,607

CATHODE RAY OSCILLOGRAPH CONTROL Filed April 7, 1934 Inventor":

Wilfred FTS eats Hus Attorne Patented Jan. 1.193s

' PATENT OFFICE nasaeo'z osrnona an oscnaocasrn com-nor.

- wan-ea F. sum, scone, N. m, assignor to General Electric Company, acorporation of New York Application April "I, 1934, Serial No. 719,534

10 Claims.

invention relates to 'cathode ray oscillographs and more particularly toa method of controlling the initiation. oi operation of such a device. tIt is often desirable to have an oscillograph set into operation bymeans associated with the occurrence of phenomena to be recorded sincethis insures a complete record' of the phenomena. Accordingly, an objectof my invention is to insure that the cathoderay oscillograph begins itsoperation at a time which is consistent with the occurrence oi thephenomena to be recorded thereby.

Another .object of the .invention is to provide means associated withthe phenomena to be recorded, of .a simple and faithful character, toinsure the discharge at the proper time, of a spark gap which sets theoscillograpli into operation. a

A better understanding 0! the invention can be had and further objectsof the invention will appear from the following specification taken in,-

connection with the accompanying drawing in which Fig. 1 is a schematicrepresentation of my 26 invention, and Fig. 2 shows a curve to. bereferred to in explaining my invention. The curve shown in Fig. 2'consists of a portion 50 to 51 which represents the arcing voltage of acircuit interrupter designated in Fig. 1 by. the numeral '14.;Therapidly increasing recovery voltage of this interrupter is shown in Fig.2-by the position of the curve between 51 and 52. It will be obviousthat while my invention is shown in connection with a polypha'se system,it is equally applicable to a single phase system. v

In order to obtain a record of this rapidlynincreasing r covery voltage,apparatus of a quickly respondin character must be used.) Such apparatusis shown schematically in Fig. l inwhich 10 designates an alternatingcurrent, generator connected tothe conductors 11, 12 and 13. Theseconductors can be short .circuited bvthe switch .ahridging contacts 15,16, 1'1 and the conductors 18 and 19. It is assumed that the circuitinterrupter is of'the automatic type which opens in changing mostrapidly which will be during the response to an overload such as wouldbe caused by the short circuit indicated; recovery voltage-o! theinterrupter 142;.

j recorded by acathode ray cscillograph 20 of the usual type with a pair01 sweep plates 39 and 40 v line voltage. The oscillograph is providedwith a} cathode 22 and an anode 9 at ground potential;

The cathode ray osoillograph 20 is energized by means of a separatesource of supply. This source comprises an alternator 31 which suppliestwo condensers 28 and 29 through a transformer 32 and rectifiers 33 and34. The oscillograph side 5 of the condensers is connected to aresistance 30 which is grounded. Connected in parallel to thisresistance is a resistance 35 and a condenser 38, the condenser 38energizing the sweep plates 39 and 40. The condenser 38 is protectedfrom over- 10 charge by thespark gap 37. The resistance 36 prevents thereturiroi the electron beam.-

The oscillograph is actuated responsive to the phenomena to be recorded.To accomplishthis there is connected across the supply side of the 15condensers 28 and 29 a spark gap comprising spheres 25 and 26 betweenwhich spheres there is a third electrode or sphere 24. i This middlesphere is connectedthrough a switchsl to the. secondary of an easilysaturable current trans-. former 23' responsive to the current inline-l3.

The switch 41 is operated through mechanical interconnection by themovemento'i' the interrupter 14. The relationship between the movemeritsof these two switches is adjustable by means of the set screw 44 whichallows the bridging member 43 to be moved relative to the switchcontacts 42.

Transformer 23 which is employed to impress a voltage on the midsphere24 is of the easily saturable type so that during the part of the cycleof the current in the'llne when the current is high,' the core of theormer will be saturated. Hence although the primary current maybe'changing at a high rate at this time, the flux 35 Vin the core willremain practically constant and no voltage'will be induced in thesecondary of thetransiormer. when the current has decreased in theprimary to a. pointwhere the core is no longer'saturated, a large fluxchange in the core 49 will begin to take place and a correspondinglyhigh voltage will be induced in the secondary. The highest voltage .willbe induced in the secondary at the time the fiux in the .core 12 timethe current is through zero. '-By zero current I mean the current at,zero and also the current within the hall cycle preceding zero which isin the unsaturated portion of the current curve. v As the circuitinterrupter opens contacts 41 and 42 will be closed and any voltageinduced in the secondary of current transformer 23 will then be conveyedto sphere 24. The operation or the a will be obvious to those havedescribed device the art from the 2 neeaeor foregoing description, butfor the purpose of rendering the description complete, I shall describethe operation as follows:

The condensers 28 and 29 which are connected to assist each other areconstantly charged from the alternator 31 but do not normally have acharge sumcient to cause a breakdown between the spheres 25 and 26. Themid-sphere 24 is so arranged that when a proper voltage is induced inthe secondary'winding of the transformer 23 and the switch 41 is closed,the gap between spheres 25 and 26 will be broken down. This inducedvoltage can be impressed directly on the sphere 24or can first beamplified in any well known manner such as for example by thermionicvalves. The switch 41 is so adjusted relative to the interrupter 14 thatthe switch 41 is closed at any time during the half cycle preceding thelast current zero which is in the saturated portion of the currentcurve.

This relationship between the switch 41 and interrupter 14 is necessaryto insure a complete record of the recovery voltage. The voltagerecorded by the oscillograph will include the part from 51 to 52 of thecurve of Fig. 2.

The breakdown of the air gap between spheres 25 and 26 efiects thedischarge of the condensers through the resistance 30. The voltage dropacross the resistance 30 impresses a negative voltage on the cathode 22causing it to emit electrons; The electrons will be deflected by theplates ,39, 40 and 21 to indicate the recovery voltage characteristicsdesired to be examined.

While I have described a particular embodiment of my invention, it willbe obvious to those skilled in the art that various modifications may bemade without departing from the spirit of my invention, and, I,therefore desire to cover all such modifications as fall within thescope of my invention by the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination with a cathode ray oscillograph', a source ofalternating current and means including a current transformer saturablewithin the normal range of variation of said alternating current andinfluenced by said alter-- nating current for initiating the operationof said cathode ray oscillograph.

2. In combination with a source of alternating current, means forshortcircuiting said source,

means for interrupting theshortcircuit on said.

source, a cathode ray oscillograph for determining a characteristic ofsaid source, and means associated with said shortcircuiting means andsaid interrupting means for initiating the operation of said cathode rayoscillograph.

3. In combination with a source of alternating current and meansinfluenced by said alternating current, means for shortcircuiting andinterrupting said source,,an indicating device and means operated by andin timed relation to said shortcircuiting and interrupting means forallowing the means influenced by the alternating .current to set saiddevice into operation,

4. In combination with a source of alternating current and a cathode rayoscillograph, means including a spark gap associated with said cathoderay oscillograph, and a transformer saturable within the normal range ofvariation of said alternating current and influenced by said source forcausing a discharge across the spark gap to set the cathode rayoscillograph into operation.

5. In combination with an alternating current circuit and a cathode rayoscillograph, means including a spark gap for initiating the operationof said cathode ray oscillograph, including a saturable transformerenergized from said circuit, means to shortcircuit and interrupt saidcircuit, and means operating in timed relationship with saidshortcircuiting and interrupting means for causing said transformer toimpress a breakdown voltage on said spark gap, thereby bringing aboutthe operation of said cathode ray oscillograph.

6. In combination, an indicating means normally idle, a source ofalternating current and means influenced by alternating current suppliedfrom said source for setting said indicating means into operation atsubstantially the-zero value of the cycle of said alternating current.

7. In combination with a source of alternating current and a cathode rayoscillograph, transformer means influenced by the cyclic yariation ofsaid alternating current and. a spark gap subject to the voltage of saidtransformer means to set the cathode ray os'cillograph into operation ata definite point in said cycle.

8. In combination with a source of alternating current and a cathode rayoscillograph, a satu-' rable transformer influenced by the cyclicvariation of said alternating current and a spark gap subject to thesecondary voltage of said transformer and so adjusted that it will setthe oathode ray oscillograph into operation at a selected point in thecycle of said alternating current.

9. In combination with a source of alternating current, and a cathoderay oscillograph, means for short-circuiting and interrupting saidsource and means operable in timed relationship both to said lastmentioned means and to the cyclic variation of said alternating currentto initiate the operation of the cathode ray oscillograph.

10. .In combination with an alternating current circuit and a cathoderay oscillograph for determining a characteristic thereof and means forinterrupting said current, a transformer connected to said line andsaturable during a portion of the cycle of said alternating current, aspark gap connected to said cathode ray oscillograph and means forconnecting said transformer to said spark gap during the half cycle whenit. is saturated for the last time before the circuit is interrupted,thus causing the cathode ray "oscillograph to operate when the currentin said circuit passes through zero-for the last time beforeinterruption of the circuit.

WILFRED F. SKEATS.

